Oven Roasted Leg of Lamb

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One of the easiest meals you can prepare is an Oven Roasted Leg of Lamb. Serve it up with baby potatoes and all you need is your favorite green vegetable to have a meal you’ll be talking about for weeks!

Can you believe there was a time I didn’t enjoy lamb? It’s true. Until my visit to Ireland a few years ago, I had no idea that lamb could be that delicious.

sliced leg of lamb with gravy along side whole baby potatoes and a sprig of rosemary on a white plate

Tender and flavorful, without the gaminess I had dreaded that is often thought with lamb. The truth is, lamb has come a long way, especially lamb raised in the United States.

A boneless oven-roasted leg of lamb (or bone-in if you prefer) couldn’t be easier to make and the lamb pan gravy that can be made from the drippings will make a weekend dinner a culinary event. So don’t wait to make this for Easter dinner, this roast will turn any night into a special occasion!

Table of Contents:

What ingredients do I need to make an Oven Roasted Leg of Lamb?

overhead view of ingredients to make oven roasted leg of lamb and potatoes

Let’s start by gathering the ingredients we need to make my Roasted Leg of Lamb. In Chef Speak this is called the “Mise en Place” which translates to “Everything in its Place”.

Not only does setting your ingredients up ahead of time speed up the cooking process, but it also helps ensure you have everything you need to make the dish.

For my recipe, I used a 4.5-pound boneless leg of lamb. Most boneless legs of lamb weigh between 4 and 5 pounds. Adjust the temperature according to the weight of the lamb.

Can I roast a bone in leg of lamb?

Yes, you can. It just makes slicing the lamb more challenging. But a bone-in roast always seems more flavorful to me.

*For a bone-in leg of lamb allow 20-25 per pound for a medium to medium-well roast.

How do I season an Oven Roasted Leg of Lamb?

leg of lamb coated with mustard and chopped garlic in a pan with baby potatoes around the roast

Old habits die hard, and I like to coat many of the roasts I cook with a grain of Dijon mustard before adding a layer of spices and herbs. You can use olive oil instead of mustard if you prefer.

After coating the top of the roast (fat side up) with mustard, sprinkle the chopped garlic on top of the mustard. If you like garlic, feel free to use more.

I’m roasting my boneless leg of lamb with potatoes.. You can also add additional vegetables if you have a bigger roasting pan. Carrots, onions, and parsnips would make a nice addition.

seasoned leg of lamb in a baking pan surrounded by baby potatoes

Add the remainder of your seasonings to the top of the lamb. You can season the potatoes at this time as well, either using the lamb seasonings or just sea salt and black pepper. The fresh herbs I use for my herb mixture include fresh rosemary and thyme but feel free to add your favorite herbs.

*Let the roast come to room temperature before placing in the oven, this will ensure even roasting.

roasted leg of lamb and potatoes in a baking dish

For a 4.5-pound boneless leg of lamb, roast in a 350-degree preheated oven for one hour and 45 minutes. This will give you a medium-temperature roast with just a hint of pink in the meat.

If you have a smaller or larger roast 15 minutes per pound will give you a medium-rare roast, and 20 minutes per pound will make it closer to medium- well. It’s important to use a meat thermometer to get the correct internal temperature of the lamb. Place the thermometer in the thickest part of the meat to get an accurate temperature.

The internal temperature of the lamb roast will continue to rise 7-10 degrees after it comes out of the oven.

*This is the instant-read meat thermometer that I use at home.

**Allow the roast to rest for 15-20 minutes before slicing. This will let juices flow back into the meat.

3 images showing how to make the lamb pan gravy

While the leg of lamb is resting, make the pan gravy to serve with it.

Melt two tablespoons of butter in a small saucepan
Add two tablespoons of all-purpose flour to the butter and cook over medium to low heat for 3-4 minutes to cook off the raw flour taste.
Add the pan drippings to the roux, mixing with a wire whisk. The gravy should be very thick.
Add one cup of beef stock (you can also use chicken stock) to the pan and continue to whisk. If the gravy is too thick, add more beef stock or water. If it is too thin, turn up the heat to high and allow it to reduce for 2-3 minutes.
Taste and reason the gravy as necessary. Simmer until ready to serve.

roast leg of lamb and slices with whole baby potatoes on a white platter

Now it’s time to slice the Oven Roasted Leg of Lamb. Place lamb on a cutting board and slice the roast against the grain.

The meat was unbelievably tender and mildly flavored. It couldn’t have been any more delicious. The garlic and lamb were also delicious. The pan gravy was perfectly seasoned and a delicious addition to the oven-roasted lamb. I honestly couldn’t stop eating it!

If this is your first time making a roast lamb recipe, I promise it will come out perfectly as long as you use a meat thermometer. It’s really that easy.

Recipe FAQ’s:

Should I cover the leg of lamb while roasting?

There is no need to cover a leg of lamb while roasting. If you’re slow-roasting a shoulder of lamb then you’d want to cover the roast.

How long does a boneless leg of lamb take to cook?

To roast the boneless leg of lamb to medium-rare should take about 70-90 minutes depending upon the size of your roast. The internal temperature of the roast at its thickest part should read 135-140ºF.

Do I need to let the lamb roast rest before slicing?

Yes; you do. The roast needs to rest a minimum of 15 minutes, up to 30 minutes is better. If you cut the roast without letting it rest, all the juices will run out of the roast making the meat dry and tough. Letting the roast rest, lets the juice flow back into the meat.

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